Mechanisms of Orthopnoea in Patients with Advanced COPD
- Amany F. Elbehairy1,2,
- Azmy Faisal3,4,
- Hannah McIsaac1,
- Nicolle J. Domnik1,
- Kathryn M. Milne1,5,
- Matthew D. James1,
- J. Alberto Neder1 and
- Denis E. O'Donnell1⇑
- on behalf of the Canadian Respiratory Research Network
- 1Division of Respiratory Medicine, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Ontario, Canada
- 2Department of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt
- 3Department of Sport and Exercise Sciences, Manchester Metropolitan University, Manchester, UK
- 4Faculty of Physical Education for Men, Alexandria University, Alexandria, Egypt
- 5Clinician Investigator Program, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Prof. Denis O'Donnell, 102 Stuart Street, Kingston, Ontario, Canada K7L 2V6. E-mail: odonnell{at}queensu.ca
Abstract
Many patients with severe chronic obstructive pulmonary disease (COPD) report unpleasant respiratory sensation at rest, further amplified by adoption of supine position (orthopnoea). The mechanisms of this acute symptomatic deterioration are poorly understood.
16 patients with advanced COPD and history of orthopnoea and 16 age- and sex-matched healthy controls (CTRL) underwent pulmonary function tests and detailed sensory-mechanical measurements including inspiratory neural drive (IND, diaphragm electromyography), oesophageal and gastric pressures in sitting and supine positions.
Patients had severe airflow obstruction (FEV1: 40±18%predicted) and lung hyperinflation. Regardless of the position, patients had lower inspiratory capacity (IC) and higher IND for a given tidal volume (i.e. greater neuromechanical dissociation (NMD)), higher intensity of breathing discomfort, minute ventilation (⩒E) and breathing frequency (Fb) compared with CTRL (all p<0.05). In supine position in CTRL (versus sitting erect): IC increased (by 0.48L) with a small drop in ⩒E mainly due to reduced Fb (all p<0.05). By contrast, patients’ IC remained unaltered, but dynamic lung compliance decreased (p<0.05) in the supine position. Breathing discomfort, inspiratory work of breathing, inspiratory effort, IND, NMD and neuro-ventilatory uncoupling all increased in COPD in the supine position (p<0.05), but not in CTRL. Orthopnoea was associated with acute changes in IND (r=0.65, p=0.01), neuro-ventilatory uncoupling (r=0.76, p=0.001) and NMD (r=0.73, p=0.002).
In COPD, onset of orthopnoea coincided with an abrupt increase in elastic loading of the inspiratory muscles in recumbency in association with increased IND and greater neuromechanical dissociation of the respiratory system.
Footnotes
This manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.
Conflict of interest: Dr. Elbehairy has nothing to disclose.
Conflict of interest: Dr. Faisal has nothing to disclose.
Conflict of interest: Dr. McIsaac has nothing to disclose.
Conflict of interest: Dr. Domnik has nothing to disclose.
Conflict of interest: Dr. Milne has nothing to disclose.
Conflict of interest: Dr. James has nothing to disclose.
Conflict of interest: Dr. Neder has nothing to disclose.
Conflict of interest: Dr. O'Donnell has nothing to disclose.
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- Received March 18, 2020.
- Accepted September 15, 2020.
- Copyright ©ERS 2020